1. Field of the Invention
The current invention relates to the processing of imaging data, and more specifically, but not exclusively, to the processing of imaging data used for three-dimensional (3D) displays.
2. Description of the Related Art
A stereoscopic 3D video display allows a viewer to perceive an image rendered on a two-dimensional (2D) display as a 3D image. This effect is achieved by first generating different images for the left and right eyes and then simultaneously presenting each different image to the corresponding eye. Different left and right images may be generated, for example, by recording a scene using two cameras separated by about 65 mm, which approximates the left/right ocular separation for human adults. When those images are then respectively provided to a viewer's corresponding eyes, the parallax effect of the two recording cameras is recreated, thereby allowing for the perception of depth and the appearance of three dimensionality. One exemplary way to provide different images to a user's left and right eyes is to use 3D glasses compatible with the video-rendering display. For example, in the case of stereoscopic displays, various manufacturers have provided (i) active shutter-type glasses to interleave left-eye and right-eye images and (ii) polarization-type displays, where polarization is used to respectively provide left and right eye images to viewers' eyes.
FIGS. 1A and 1B show portions of two exemplary simplified transmission paths for a 3D image, such as a single frame of a 3D video. Left-eye image 101 and right-eye image 102 represent two views of a scene and exhibit exaggerated parallax, for effect. Note that actual left-eye and right-eye images would typically look fairly similar when viewed side by side. In some newer and/or high-bandwidth systems, images 101 and 102 are kept separate throughout their transmission for display rendering. In some systems, however, images 101 and 102 are processed and combined for transmission in a 3D-compatible format via a legacy 2D transmission system and then processed again and separated for display rendering on a 3D display.
Note that, unless otherwise specified, for purposes of some exemplary descriptions herein, the images transmitted and processed correspond to raster-formatted rectangular images of 1920h×1080v pixels (where “h” and “v” stand for horizontal and vertical, respectively), which are compatible with an HDTV (high-definition television) format. Embodiments of the invention are not limited to the above dimensions or formats.
FIG. 1A shows left-eye image 101 and right-eye image 102 processed and combined, for transmission, into side-by-side (or left/right) image 103, which comprises (i) left-side image 104 and (ii) right-side image 105, where left-eye image 101 is encoded as left-side image 104 and right-eye image 102 is encoded as right-side image 105. Note that this order may be reversed. Images 104 and 105 are each 960h×1080v pixels in size. In other words, images 104 and 105 are compressed and comprise half as many pixels as images 101 and 102, respectively. This compression may be achieved, for example, by removing every other vertical line from the original image. After transmission, images 104 and 105 are processed to generate reconstructed left-eye image 106 and reconstructed right-eye image 107, respectively. The reconstructed images may be generated by methods such as pixel-doubling, interleaving, interpolation, and/or other methods for constructing decompressed images, now known or later developed.
FIG. 1B shows left-eye image 101 and right-eye image 102 processed and combined, for transmission, into top/bottom image 108, which comprises (i) top-part image 109 and (ii) bottom-part image 110, where left-eye image 101 is encoded as top-part image 109 and right-eye image 102 is encoded as bottom-part image 110. Note that this order may be reversed. Images 109 and 110 are each 1920h×540v pixels in size. In other words, images 109 and 110 are compressed and comprise half as many pixels as images 101 and 102, respectively. This compression may be achieved, for example, by removing every other horizontal line from the original image. After transmission, images 109 and 110 are processed to generate reconstructed left-eye image 111 and reconstructed right-eye image 112, respectively.
Note that side-by-side image 103, top/bottom image 108, and other formats for encoding two related images into a single combined image that preserves about half of the pixels of each original image are generically referred to herein as 3D-compatible split-screen-format images, or 3D-compatible images for short. 3D-compatible images are treated by conventional 2D devices as conventional 2D images, thereby allowing transmission of 3D-compatible images using legacy 2D devices. Problems can arise, however, because the conventional 2D devices are not aware they are processing 3D-compatible images and may overlay 2D imagery over the 3D-compatible images and thereby cause undesired results.
FIG. 2 shows the effects of an exemplary overlay on top/bottom image 108 of FIG. 1B. In FIG. 2, a 2D device, such as a legacy set-top box (STB) (not shown) overlays closed captioning (CC) region 202 over top/bottom image 108 to generate image 201. Image 201 is processed to generate reconstructed left-eye image 111, as in FIG. 1B, and reconstructed right-eye image 203, where CC overlay 202 is transformed into vertically-stretched CC overlay 204, which appears over only the reconstructed right-eye image. When a viewer sees images 111 and 203, the 3D effect would be ruined in the area of CC overlay 204. In addition, viewing a series of 3D images with an overlay over only one side's image may be unpleasant and trigger headaches for a viewer.
FIG. 3 shows the effects of an exemplary overlay on side-by-side image 103 of FIG. 1A. In FIG. 3, a 2D device, such as a legacy STB (not shown) overlays closed captioning (CC) region 302 over side-by-side image 103 to generate image 301. Image 301 is processed to generate reconstructed left-eye image 303 and reconstructed right-eye image 304. The left half of CC region 302 gets horizontally stretched into CC region 305 of left-eye image 303, and the right half of CC region 302 gets horizontally stretched into CC region 306 of right-eye image 304. This results in an incoherent 3D image since each eye's reconstructed image would have about half of the content of CC region 302, each half in a similar, but not necessarily identical, location of the respective image. Consequently, here, too, a 2D overlay layer would ruin the 3D effect and may be discomforting to view.